Au1-xNix合金(x=0.30-0.42)低温电阻率极小值的机理探讨

为了解释Au_1-xNi_x合金(x=0.30—0.42)低温出现电阻率极小值的实验结果,本文提出一个低浓度自旋集团顺磁态合金的模型,得到自旋集团孤立近似下和自旋集团耦合作用下的电阻率公式,并和晶格散射的贡献(由Au₈₀Ni₂₀合金或Au-Cu合金的ρ_i(T)实验数据代替)联合起来,得到ρ(T)的计算曲线,和实验结果符合得很好。当Tmin,电阻率随温度增高而下降,主要是自旋集团孤立近似下的Kondo效应引起的。自旋集团之间的RKKY耦合作用对电阻率的贡献在低温时大,随着温度增高按1/T规律迅速减小,所以ρ(T)-ρ_i(T)实验值在相当宽温度范围出现logT关系。随着温度增高,晶格散射对电阻率的贡献将变得重要,当T=T_min,电阻率出现极小值。关键词：

A MECHANISM OF RESISTIVITY MINIMA IN Au1-x Nix ALLOYS (x = 0.30-0.42)

In order to explain the experimental results of resistivity minima in Au_1-xNi_x alloys (x=0.30-0.42) at low temperature, we propose a model of the alloy with dilute spin clusters in the paramagnetic state based on the s-d interaction. The resistivity contribution from the electron scattering by isolate spin clusters and by spin clusters with a ferromagnetic RKKY interaction are considered. Combining with the phonon contribution, derived from the experimental data of ρ_i(T) of Au-Cu or Au₈₀Ni₂₀ alloy, we obtain a resistivity minimum. The calculated total resistivity ρ(T) is in good agreement with the experimental result. It is shown that a decrease in ρ with increasing temperature below T_min is mainly attributed to the Kondo effect caused by isolate spin clusters. The electron scattering from coupled spin cluster pairs gives a much smaller contribution to the resistivity, which exhibits a T^-1 temperature-dependence and decreases rapidly with increasing temperature. So the experimental relults of ρ(T)-ρ_i(T) in Au_1-xNi_x alloys (x=0.30-0.42) show a log T temperature-dependence over a wide tempera-ture range.